This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The purpose of this study is to identify and characterize regions of the human brain that are differentially reactive to ovarian sex steroids and to determine if regional cerebral metabolism differs in women with premenstrual syndrome as compared with controls.